While the present invention will be described in a specific manner as being applicable to a pacemaker, it will be understood that the invention is applicable to any other type of implantable medical device intended to stimulate body tissue.
Modern pacemakers monitor the activity of a heart and provide a stimulation pulse in the absence of normal heart activity. Advantageously, such devices are relatively small, light-weight and implantable. In order to sense and stimulate the heart, however, such pacemakers must be used with a pacemaker lead, an electrical conductor that carries electrical signals between the heart and the pacemaker. Advantageously, the pacemaker lead can be inserted into the heart transvenously through a relatively simple and well-known surgical procedure. Disadvantageously, one end of the lead (designated herein as the “connecting end”) must be electrically and mechanically secured to the pacemaker in a way that provides for a long-term safe and secure, yet detachable connection. Those skilled in the pacemaker art have long sought for a simple, yet reliable and safe, technique for making this detachable electrical and mechanical connection between the pacemaker device and the connecting end of the pacemaker lead.
In order to appreciate the advantages of the present invention, it will help first to have a basic understanding of the manner in which the mechanical and electrical connection functions are carried out in known pacemakers. The main components associated with the connection function of such known pacemakers are shown diagrammatically in FIG. 1. A pacemaker 10 electrically includes a battery 14 that powers electrical circuits 12. The pacemaker electrical circuits 12 and battery 14 are mechanically enclosed and hermetically sealed in a suitable housing 16. Typically, this housing or case 16 is shaped to include a flat side or platform 20 to which a suitable epoxy connector 22 can be bonded. At least one feedthrough terminal 18, in electrical contact with the electrical circuits 12, passes through the case or housing 16 and protrudes beyond the platform 20. This feedthrough terminal 18 is electrically isolated from the case 16. A platinum wire 24, or other suitable conductive element, connects the terminal 18 to a conductive connector block 26 that is fitted within the connector 22. A pacemaker lead 28, having a proximal electrode 30, connects to the pacemaker electrical circuits by inserting the proximal electrode 30 into a receiving channel 31 of the connector 22 until the electrode 30 is in contact with the connector block 26. A set screw 32 is then securely tightened using a torque wrench 34 to firmly hold the electrode 30 in both mechanical and electrical connection with the connector block 26. A septum, not shown but having the construction generally described in commonly assigned U.S. Pat. No. 5,509,928 issued Apr. 23, 1996 to Acken, is typically placed over the set screw 32 in order to prevent body fluids from seeping through the set screw hole. Further, sealing ribs or ridges 36 on the connecting end of the pacemaker lead are designed to tightly engage the inside edges of the receiving channel 31 in order to prevent any body fluids from entering into the receiving channel 31 once the connecting end of the lead has been inserted into the connector 22.
While the descriptions presented in the prior art vary greatly relative to, for example, different types of locking mechanisms for performing the mechanical connection function, or different types of arrangements for performing the electrical feedthrough function, including the use of bipolar or multiple pacemaker leads, all such systems include the use of a premolded or cast connector 22 that is bonded to a sealed pacemaker housing 16 in which the electrical circuits are located.
Typically, prior art connectors 22 are cast in place from epoxy to the platform or header 20 of the pacemaker, or a premolded connector is bonded to the platform 20 using a suitable sealing and bonding agent. Further, once the electrical connection is made from the terminal post 18 to the connector block 26, and the connector is attached to the housing, all remaining voids within the connector 22, not including the receiving channel 31 into which the proximal end of the pacemaker lead 28 is to be inserted, must be filled with a suitable filler material, such as a two-component epoxy or silicone rubber.
In summary, then, of the foregoing narrative, it can be said that pacemakers and other implantable devices such as cardiac defibrillators require a method of passing electrical signals between the device and the heart. To transmit signals from the device to the heart, implantable leads are used which make electrical contact with the device through the connector top ring and tip contacts. The signals are then transmitted from the device to the heart via the implantable leads. To ensure an uninterrupted electrical path between the device and the heart, a strong reliable mating between each implantable lead and the connector contacts of the device is necessary. It is also desirable to secure the leads in place once they are inserted into the device. To achieve these connector conditions, external calibrated torque wrenches are typically used to secure the leads in place by means of setscrews or compression of seals. The use of external tools for achieving connector conditions has created reliability problems such as cored septum, stripped wrench and hex and the like. Further, time is required to ensure electrical contact while the tool is being used.
There are numerous patents which are generally illustrative of the state of the art relating to electrical connector systems used with implantable medical devices. For example, U.S. Pat. No. 5,951,595 issued to Moberg et al. discloses a connector assembly which employs an actuator mechanism for fixing and sealing electrical leads inserted into lead receptacles within the connector assembly without the use of setscrews. Typical of constructions of connector systems operable to frictionally engage the connector pin of an implantable lead are U.S. Pat. No. 5,070,605 to Daglow et al.; U.S. Pat. No. 5,275,620 to Darby et al.; U.S. Pat. No. 5,514,172 to Mueller; and U.S. Pat. No. 6,029,089 to Hawkins et al. U.S. Pat. Nos. 5,300,108 and 5,514,173 to Rebell et al. disclose active fixation leads which are extended and retracted by means of a compound screw which employs ball bearings for its operation. U.S. Pat. No. 5,354,326 to Comben et al. discloses a connector for establishing an external connection with multiple conductor implantable leads utilizing a unique twist lock design. U.S. Pat. No. 5,730,628 to Hawkins discloses a multi-contact connector for an implantable medical device using a plurality of flat spring contacts for mating electrical engagement with the electrical lead. U.S. Pat. No. 6,183,305 to Doan et al. discloses a connector assembly which employs a bayonet type interlocking construction for removably securing a connector pin of an electrical lead.
It was with knowledge of the foregoing state of the technology that the present invention has been conceived and is now reduced to practice.